Iodopropargyl compounds, i.e. compounds containing a propargyl group and an iodine on the acetylenic carbon, are known to be useful in controlling bacteria and fungi in various aqueous systems. U.S. Pat. Nos. 4,259,350; 4,719,227; 4,616,004; 3,923,870; 4,592,773 give various examples of iodopropargyl compounds with microbicidal properties. The disclosure of each of these patents identified in this paragraph is incorporated specifically herein by reference.
One such iodopropargyl compound is iodopropargyl carbamate manufactured by Buckman Laboratories, Inc. as BL-1120 product. The preparation and use of iodopropargyl carbamate as a microbicide and a preservative is described in U.S. Pat. No. 4,945,109, the disclosure of which is incorporated herein by reference.
Another such iodopropargyl compound is 3-iodopropargyl-N-butylcarbamate (IPBC). This compound is manufactured and sold by Troy Chemical Company under various names such as Polyphase product, Polyphase AF-1 product, Polyphase NP-1 product, etc. IPBC is used in the metalworking fluid industry for controlling bacteria and fungi.
Although good microbicides, iodopropargyl compounds are expensive. Systems requiring high concentrations of iodopropargyl compounds are generally uneconomical.
Hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine has been used in the metalworking fluid industry for a long time. This compound is sold as Grotan product, Busan 1060 product, etc. This compound is known in the art as "triazine".
As can be seen in Table 1 (see Samples 14-17), high concentrations of hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine are required to control both bacteria and fungal growth in metalworking fluids.
One of the by-products of hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine when used as a microbicide is formaldehyde. Because of the carcinogenic properties of formaldehyde, it is desirable to use compounds that produce formaldehyde in the smallest quantities possible. Unfortunately, when used in reasonable concentrations, i.e., concentrations which produce only small amounts of formaldehyde, triazines are ineffective against fungi.
Both of these types of products are used alone to control microorganisms in industrial fluids. Many industries, such as the machining industry, experience problems caused by microorganisms. Aqueous metalworking fluids or cutting fluids used in the machining industry are particularly susceptible to fouling caused by microorganisms. In machining operations, metalworking fluids are used primarily to reduce friction and heat, thereby reducing wear and prolonging the life of equipment.
Unfortunately, metalworking fluids have properties which are ideal for the growth of bacteria and fungi. Although bacteria are important in the biodeterioration of metalworking fluids, fungi and yeast play an important role as well. (Bennett, E. O., "The Deterioration of Metalworking Fluids", Prog. Industrial Microbiology, 13:121 (1974)).
Disadvantageously, these microorganisms can cause the buildup of slime/microbial deposits on machine surfaces, the clogging of jets and lines, the deterioration of the properties of the metalworking fluid itself, enhanced corrosion, and health and odor problems. When deteriorated by the growth of microorganisms, the metalworking fluid begins to deteriorate and lose many of its essential properties. The pH of the fluid may drop and other chemical changes may occur until the fluid can no longer provide adequate lubrication. At this point, the fluid must be replaced with fresh fluid, which is costly and results in loss of production time.
The previously-mentioned problems have resulted in the extensive use of biocides in metalworking fluid systems. Biocides may be incorporated in fluid concentrate or added to diluted fluids once they are in the holding tanks of the machine works.
There are many commercially available biocides, at least many of which disadvantageously have odor problems, or create hazards with respect to storage, use or handling, which limit the utility thereof. Consequently, workers in the art have continued to seek improved biocides.
Economic factors, particularly the cost of the biocide and the expense of its application, can also be important when choosing a particular biocide for use in metalworking fluid systems. The cost performance index of any biocide is derived from the basic cost of the material, its effectiveness per unit weight, the duration of its biocidal or biostatic effect in the system treated, and the ease and frequency of its addition to the system treated.
Workers in the art have sought a commercially available biocide capable of exhibiting a prolonged biocidal effect at normal use levels. Physical conditions, such as temperature and chemical reactivity with ingredients present in the system, often diminish or eliminate the effectiveness of prior art biocides known to the inventors. For example, many systems contain organic material which may react with a specific: biocide or render it ineffective.
Metalworking fluid systems in which heavy microbial growth occurs can benefit from the practice of the present invention, which is described below. The practice of the present invention can also benefit many other aqueous systems, whether or not heavy microbial growth occurs, because it provides a more limited use of hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine, a formaldehyde-producing biocide.